It is known that light alloy wheels are not always the first equipment of an automobile. Indeed, very often alloy wheels are mounted in replacement of the standard steel wheels. There is also a rather broad market, especially for high-performance cars, in which the original light alloy wheels are replaced with others of a more refined design.
The maker of alloy wheels must therefore provide his products to meet the dimensional requirements imposed by the various automobiles.
In addition to the two basic dimensions consisting of the diameter and width of the wheel, a measurement which must be taken into consideration with the greatest attention is the distance between the striker surface of the wheel on the hub and the median plane of the wheel. Even for the same diameter and width, wheels of different cars often differ in said distance.
To meet the various requirements, the wheel maker is thus forced to provide and keep in store a very broad range of wheels. This is particularly costly for large-diameter wheels designed for high-performance sports cars. In this case, the design refinement of the cars makes it necessary for practically each car type to have its specific wheel. In addition, each wheel has a rather high value. Finally, the quantities of such cars in existence and hence the market for their wheels are of course very limited.
There is thus the problem of providing a wheel assembly which can be used on several automobiles.
There are known (FR-A-1549438, GB-A-2080745) adapters which permit mounting the spare wheel of a motor vehicle on the hub of a trailer having couplings different from those of the automobile. These adapters comprises an intermediate disc with bores designed for fixing on the studs of the trailer hub and with studs designed for fixing of the motor vehicle wheel.
There is also known (GB-A-577095) a wheel for agricultural tractors provided in two parts, i.e. an external part made in various sizes and forms to be able to carry various tires or special rims, and an internal portion which can also be made in various sizes and forms suited for mounting on different hubs. The two parts are coupled together by means which ensure their interchangeability.
In addition, among light alloy wheels, wheels whose design resembles the single-nut wheels used in competition, i.e. wheels having a single central fixing nut in place of the normal four or five nuts, are much more appreciated due to their sporty appearance. Naturally these are not truly single-nut wheels. Indeed, their central `nut` is merely a shaped cap covering the normal fixing nuts.